Abstract

A continuous self-cleaning drilling fluid tank includes a liquid impervious receptacle having a bottom and a peripheral sidewall. Unprocessed drilling fluid requiring reconditioning are diverted into the receptacle. A processed drilling fluid outlet is provided, whereby reconditioned drilling fluid passes from the receptacle. A plurality of scraper blades are provided which are carried by a continuous loop conveyor positioned immediately adjacent to the bottom. A sludge outlet is provided, whereby sludge passes from the receptacle. The continuous loop conveyor is driven to cause the scraper blades to scrape sludge resting on the bottom toward the sludge outlet.

Description

FIELD OF THE INVENTION

The present invention relates to a drilling fluid tank used in earth drilling and, in particular, the drilling of oil and gas wells.

BACKGROUND OF THE INVENTION

In earth drilling, drilling fluid is pumped down the drill string; exiting through nozzles in the drill bit. As pumping continues, the drilling fluid flows up an annular space on the outside of the drill string carrying cuttings to surface. While the circulation of drilling fluid keeps the bottom of the well bore clear of cuttings, it also plays a vital role in well control as the column of drilling fluid serves to contain well bore pressure. The viscosity of the drilling fluid must be suited to well bore pressure. The composition of the drilling fluid (oil based, water based) must be suitable for the type of oil bearing or gas bearing formation.

The drilling fluid is prepared in accordance with directions given by a qualified expert. Due to the volume of drilling fluid used, it is recycled. The recycling process involves passing the drilling fluids through shakers and other devices to remove large cuttings. The drilling fluids are then diverted to a drilling fluid tank to be “reconditioned” to the desired viscosity and other characteristics.

When drilling fluid is returned to the drilling fluid tank, a settling occurs. Fines from the cuttings which were mixed with the drilling fluid, begin to settle out forming a sludge on the bottom of the drilling fluid tank. Periodically this sludge must be removed using a vacuum truck. The suction of the sludge from the drilling fluid tank by the vacuum truck invariably removes some of the drilling fluid and affects the chemical balance of the drilling fluid in the drilling fluid tank. Every time this occurs, the volume of drilling fluid removed must be replaced and additional chemicals added.

SUMMARY OF THE INVENTION

What is required is a drilling fluid tank that is capable of continuous self-cleaning.

According to the present invention there is provided a continuous self-cleaning drilling fluid tank which includes a liquid impervious receptacle having a bottom and a peripheral sidewall. Means are provided for diverting unprocessed drilling fluid requiring reconditioning into the receptacle. A processed drilling fluid outlet is provided, whereby reconditioned drilling fluid passes from the receptacle. A plurality of scraper blades are provided which are carried by a continuous loop conveyor positioned immediately adjacent to the bottom. A sludge outlet is provided, whereby sludge passes from the receptacle. Means are provided for driving the continuous loop conveyor to cause the scraper blades to scrape sludge resting on the bottom toward the sludge outlet.

With the drilling fluid tank, as described above, sludge is continuously been directed by the scraper blades to the sludge outlet.

Although beneficial results may be obtained through the use of the drilling fluid tank, as described above, the addition of unprocessed drilling fluid into the drilling fluid tank can cause turbulence which retards the settling out of fines from the drilling fluid. Even more beneficial results may, therefore, be obtained when the means for diverting unprocessed drilling fluid requiring reconditioning into the receptacle is a spray manifold which is adapted to spray unprocessed drilling fluid onto a surface of drilling fluid in the receptacle.

Although beneficial results may be obtained through the use of the drilling fluid tank, as described above, it is preferred that a paddle system be provided which is adapted to carry sludge out of the receptacle through the sludge outlet. The use of paddles has been found to perform better than a gravity feed through the use of an inclined plane or other feed mechanisms.

Although beneficial results may be obtained through the use of the drilling fluid tank, as described above, the use of a pump to remove reconditioned drilling fluid causes undesirable turbulence which retards settling of fines. Even more beneficial results may, therefore, be obtained when the drilling fluid outlet extends through the peripheral sidewall adjacent to the bottom and the drilling fluid outlet has an upwardly extending feed pipe. With this configuration, drilling fluid spills into the feed pipe and flows by force of gravity through the drilling fluid outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein:

FIG. 1 is a perspective view of a continuous self-cleaning drilling fluid tank constructed in accordance with the teachings of the present invention.

FIG. 2 is a side elevation view, in section, of the drilling fluid tank illustrated in FIG. 1.

FIG. 3 is a top plan view of the drilling fluid tank illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment, a continuous self-cleaning drilling fluid tank generally identified by reference numeral 10, will now be described with reference to FIGS. 1 through 3.

Structure and Relationship of Parts:

Referring to FIG. 1, drilling fluid tank 10 includes a liquid impervious receptacle 12 having a bottom 14 and a peripheral sidewall 16. Referring to FIGS. 2 and 3, in the illustrated embodiment, a spray manifold 18, adapted with slots 20, sprays unprocessed drilling fluid 22 onto a drilling fluid surface 24 within liquid impervious receptacle 12. A processed drilling fluid outlet 26 extends through peripheral sidewall 16 adjacent to bottom 14 whereby reconditioned drilling fluid passes from liquid impervious receptacle 12. Referring to FIG. 2, processed drilling fluid outlet 26 has an upwardly extending feed pipe 28 which allows drilling fluid to spill into feed pipe inlet 30 and flow, by force of gravity, out of liquid impervious receptacle 12 through processed drilling fluid outlet 26. In the illustrated embodiment, processed drilling fluid outlet 26 is further adapted with a pivotal joint 32 allowing for angular adjustment of upwardly extending feed pipe 28. Referring to FIGS. 1 through 3, a plurality of scraper blades 34 actuated by a continuous loop conveyor 36 circulate within liquid impervious receptacle 12 such that scraper blades 34 are positioned immediately adjacent to bottom 14 as illustrated in FIG. 2. Referring to FIG. 3, in the illustrated embodiment, continuous loop conveyer 36 is in the form of two continuous loop chains 38 transported by several transverse rollers 40 such that plurality of scraper blades 34 extend transversely between continuous loop chains 38. In the illustrated embodiment, liquid impervious receptacle 12 is further adapted with a paddle system 42 and a sludge outlet 44, by which sludge is propelled from liquid impervious receptacle 12. Referring to FIGS. 1 through 3, continuous loop conveyor 36 and paddle system 42 are driven by a drive motor 46 which causes scraper blades 34 to scrape sludge resting on the bottom toward paddle system 42 and sludge outlet 44.

The remaining aspects of continuous self-cleaning drilling fluid tank 10, not directly related to the inventive concept, will now be described. Referring to FIG. 2, liquid impervious receptacle 12 is further adapted with a chemical treatment unit 48, ladder 50, railing 52 and skid 54.

Tank 12 is primarily a settling tank. As fines settle out of the drilling fluids, they form sludge on bottom 14 of tank 12. The present invention permits the continuous removal of sludge from tank 12 as it settles. In addition, the present invention accommodates the continuous entry of unprocessed drilling fluids and the continuous exit of processed drilling fluids, without disrupting the settling process. The entry of drilling fluids is accommodated by spraying them lightly onto the surface of liquid within tank 12. The removal of drilling fluids is accomplished by a gravity feed through a skimmer pipe.

In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the claims.

Claims (8)

1. A continuous self-cleaning drilling fluid tank, comprising:

a liquid impervious receptacle having a bottom and a peripheral sidewall;

a plurality of scraper blades carried by a continuous loop conveyor positioned immediately adjacent to the bottom;

a sludge outlet, whereby sludge passes from the receptacle; and

means for driving the continuous loop conveyor to cause the scraper blades to scrape sludge resting on the bottom toward the sludge outlet.

2. The drilling fluid tank as defined in claim 1, wherein the means for diverting unprocessed drilling fluid requiring reconditioning into the receptacle is a spray manifold which is adapted to spray unprocessed drilling fluid onto a surface of drilling fluid in the receptacle.

3. The drilling fluid tank as defined in claim 1, wherein a paddle system is provided which is adapted to direct sludge out of the receptacle through the sludge outlet.

4. The drilling fluid tank as defined in claim 1, wherein the drilling fluid outlet extends through the peripheral sidewall adjacent to the bottom, the drilling fluid outlet having an upwardly extending feed pipe, such that drilling fluid spills into the feed pipe and flows by force of gravity through the drilling fluid outlet.

5. A continuous self-cleaning drilling fluid tank, comprising:

a liquid impervious receptacle having a bottom and a peripheral sidewall;

a spray manifold which is adapted to spray unprocessed drilling fluid requiring conditioning onto a surface of drilling fluid in the receptacle;

a processed drilling fluid outlet extending through the peripheral sidewall adjacent to the bottom, whereby reconditioned drilling fluid passes from the receptacle, the drilling fluid outlet having an upwardly extending feed pipe, such that drilling fluid spills into the feed pipe and flows by force of gravity through the drilling fluid outlet;

a plurality of scraper blades carried by a continuous loop conveyor positioned immediately adjacent to the bottom;

a sludge outlet, whereby sludge passes from the receptacle; and

a drive motor for driving the continuous loop conveyor to cause the scraper blades to scrape sludge resting on the bottom toward the sludge outlet; and

a paddle system adapted to direct sludge out of the receptacle through the sludge outlet.

6. The drilling fluid tank as defined in claim 5, wherein the feed pipe for the drilling fluid outlet is pivotally mounted to permit angular adjustment.